Community antenna television (“CATV”) systems provide a premise with many services including, but not limited to, Internet service, telephone service (e.g., voice-over-Internet protocol (“VOIP”) telephone), television service, and music service. Each of these services requires the CATV system and the premise to exchange bandwidth, such as, for example, radio frequency (“RF”) signals, and digital signals, among many others. Typically the CATV system is configured to use bandwidths that are separated from one another for the purpose of grouping transmissions, and more often the grouping is by the direction that the transmission are transmitted or received in the CATV system. That is, transmissions that have one frequency may be transmitted or received relative to the premise and/or the head-end of the CATV system in a direction that is different from transmissions that have a second frequency. As one example, transmissions that originate from the head-end facility and are transmitted to the premise are referred to herein as a downstream bandwidth, while transmissions that originate from the premise and are transmitted to the head-end facility are referred to herein as an upstream bandwidth.
FIG. 1 illustrates one example of a CATV system 100 that includes a head-end facility 102 and a local network 104, which are connected to the head-end facility 102 by distribution lines 106. The local network 104 includes a feed tap 108, a drop-line 110, and a portion 112 with a premise 114. The premise 114 is connected to the head-end facility 102 via the combination of the distribution line 106, the feed tap 108, and the drop-line 110. The system 100 further includes a downstream bandwidth 116 and an upstream bandwidth 118, both of which are discussed in more detail below.
Typically the downstream bandwidth 116 and the upstream bandwidth 118 are defined by upper and lower cutoff frequencies. Exemplary frequencies for the downstream bandwidth 116 are more than about 54 Mhz, and in one application can be from about 54 Mhz to about 1002 Mhz. Frequencies for use as the upstream bandwidth 118 are less than about 40 Mhz, and in one application can be from about 5 Mhz to about 40 Mhz.
The terms “downstream bandwidth,” and “upstream bandwidth” are used herein to generally describe some of the transmissions that are transmitted, exchanged, and manipulated within systems such as the CATV system 100. As is inherent in systems such as system 100, these terms are used in a manner that describes any number of transmissions. Moreover, each of the transmissions that are described by these terms may exhibit properties that are similar to, or different from, other the properties of other transmissions. These other transmissions can also be classified by the terms “downstream bandwidth,” and/or “upstream bandwidth” as used in connection with the various embodiments of the present invention that are disclosed, described, and contemplated herein.
In addition to CATV systems, systems that are configured similar to the system 100 of FIG. 1 include, but are not limited to, other uni-directional, and bi-directional communication systems that communicate with remote premises, e.g., premise 114. Similar systems may conduct the transmissions via transmission lines, e.g., distribution lines 106, and drop lines 110. Transmission lines of the type used as the transmission lines are typically transmission-carrying conductors such as, for example, coaxial cable, shielded cable, multi-core cable, ribbon cable, and twisted-pair cable, among others.
Premises that are connected to the system 100 such as the premise 114 include, for example, homes, apartments (e.g., individual apartments, and/or townhomes), and businesses. These premises can have any number of devices and or appliances (collectively, “premise devices”) that are coupled either directly or indirectly to the drop-line 110. Techniques and equipment that are used to connect each of the individual premise devices to the head-end facility 102 are generally well-known to those familiar with CATV systems, and therefore a detailed discussion is not provided for purposes of the present discussion.
The premise devices can include, but are not limited to, modems, desktop computers, notebook computers, televisions, gaming consoles, set-top-boxes (STB), and set-top-units (STU), among many others. These are generally configured to communicate with the head-end facility 102, via the downstream bandwidth 116 and the upstream bandwidth 118. For example, the premise devices typically receive the downstream bandwidth 116 from the head-end facility 102, and can transmit the upstream bandwidth 118 to the head-end facility 102.
During periods of normal operation, systems such as the CATV system 100 conduct transmissions that are found within the frequency bands discussed above. It is recognized, however, that the scope, construction, and general breadth of the CATV system 100 makes these systems susceptible to transient events such as, for example, lightning strikes, power outages, and switching events. These transient events can generate inputs (hereinafter, “surge inputs”) that fall outside of the frequency bands for the upstream bandwidth and the downstream bandwidth. Moreover, it is common that the transient events can generate surge inputs that fall into frequency bands that are below 1 Mhz. For example, if a component of the CATV system is struck by lightning, the surge inputs typically have a frequency that is less than about 1 Mhz, and energy levels that are sufficient to damage the premise devices.
Surge inputs like the ones discussed above are harmful to many electrical components, and particularly harmful to premise devices that are connected to the CATV system. It is therefore preferable to provide some type of surge protection device, which is designed to prevent damage to the premise device. However, a prerequisite for any such surge protection device is that it should also pass transmissions that are found in the desired frequency bands, such as, for example, the frequency bands of the downstream bandwidth and the upstream bandwidth.
Many surge protection devices are implemented in series between the part of CATV system where the surge input originates and the premise devices. Unfortunately, these devices typically do not prevent the surge input from reaching the premise device. Rather the devices (e.g., gas discharge tubes (“GDTs”) and/or metal oxide varisters (“MOVs”)) are invariably constructed with a built-in delay, or response time. This delay allows the surge input to momentarily reach the premise device before the device is fully activated to completely protect the premise device from the surge input. Such delay is inherently detrimental because the slower the response time, the more likely it is that damage will occur to the premise device.
Therefore, a surge protection device is needed that can prevent the surge input from reaching the premise device, and more particularly, a surge protection device is needed that it is fully activated so as to provide complete protection from the surge input. It is also desirable that the surge protection device is constructed in a manner so as to increase its life expectancy, and to reduce the need for maintenance and/or replacement after the transient event occurs in the CATV system.